The present invention relates to an open-loop drive control for sheet-fed printing machines having a multiplicity of printing units (printing mechanisms). Each printing unit includes cylinders that are mechanically coupled to each other. In particular, a feeder, transfer rollers, printing cylinders and rubber cylinders are coupled to each other as a sheet-travel module. The printing units further include plate cylinders, inking systems, and a delivery assembly, and are driven by an electrical drive.
Sheet-fed printing machines generally include a plurality of printing units, which are mechanically coupled to each other in a roller system. In this context, each printing unit has associated to it an inking system, which acts upon a plate cylinder. Every plate cylinder is mechanically coupled to a rubber cylinder and, via the latter, to a printing cylinder. The printing cylinders of individual printing units are in mechanical contact with each other via so-called transfer rollers. The first printing cylinder for its part is mechanically coupled to a feeder, the last printing cylinder to a delivery assembly. In one conventional sheet-fed printing machine, each printing unit is mechanically coupled to the aforementioned specific cylinders as a so-called sheet-travel module.
In one conventional sheet-fed printing machine, all the cylindersxe2x80x94in the form of rollersxe2x80x94that participate in the paper guidance and in the printing are mechanically coupled via a traversing wheel train or a vertical shaft. FIG. 1 shows the design of a sheet-fed printing machine of this type having four printing units 1 through 4. The system is depicted in a cross-section of individual cylinders. Four printing units 1 through 4 are illustrated, having, respectively, inking system F1 through F4, plate cylinder P1 through P4, rubber cylinder G1 through G4, and printing cylinders D1 through D4, which are connected via transfer rollers T2 through T4. In addition, a feeder AN and a delivery assembly AB are shown.
Conventionally, a mechanical interconnection of this type of sheet-fed printing machine is moved by a central electrical drive. However, the cylinders that are coupled in this manner represent a vibratory multiple-mass system. Thus, vibrations can affect the printing precision negatively. As a result, the number of printing towers or printing units that can be included in the mechanical interconnection is limited.
In a conventional sheet-fed printing machine having the mechanical interconnection described involving a central drive, the dynamic positional deviation with respect to a setpoint value continually increases from printing unit to printing unit due to the elasticity of the multiple-mass system. Thus, precision is dependent on the number of printing units. In the case of a prescribed mandatory level of precision, it follows that the number of printing units is limited.
An object of the present invention is to provide a drive control for a sheet-fed printing machine having a multiplicity of printing units which avoids the problem of the dynamic positional deviation increasing from printing unit to printing unit, delivers a higher level of precision, and in addition makes it possible to realize a greater number of printing units in the mechanical interconnection. A further object is to provide a corresponding method for the drive control.
According to the present invention, in an open-loop drive control for sheet-fed printing machines of the type discussed above, for example, the mechanical coupling of the individual cylinders AN, T1 . . . T4, D . . . D4, G1 . . . G4, P1 . . . P4, F1 . . . F4, AB is at least partially removed and provision is made in the de-coupled cylinders for further electrical drives MP1 . . . MP4, MG1 . . . MG4, which, in each case, have an assigned separate closed-loop control R_MP1 . . . R_MP4, R_MG1 . . . R_MG4, all closed-loop controls R_MP1 . . . R_MP4, R_MG1 . . . R_MG4 obeying a common reference variable A_Soll.
A method is also provided for the open-loop drive control for sheet-fed printing machines in which the mechanical coupling of individual cylinders AN, T1 . . . T4, D1 . . . D4, G1 . . . G4, P1 . . . P4, F1 . . . F4, AB is at least partially removed and the decoupled cylinders are electrically driven independently of each other, there being, in each case, an assigned separate closed-loop control R_MP . . . R_MP4, R_MG1 . . . R_MG4, each closed-loop control R_MP1 . . . R_MP4, R_MG1 . . . R_MG4 obeying a common reference variable A_Soll.
The present invention, which, for example, partially removes the mechanical interconnection of the sheet-travel modules of individual printing units and replace it with individual drives, offers the advantage that as a result of a multi-motor open-loop drive control, the fault does not continue to increase from printing unit to printing unit, since at each printing unit the torque is supplied separately, and all the drives are closed-loop controlled at the same reference variable.
In one embodiment of the present invention, the coupling between the rubber cylinders and the plate cylinders is removed and is replaced by individual drives in the rubber cylinders and the plate cylinders.
A further advantageous embodiment of the present invention prescribes a common reference variable through a reference variable interpolator, which continually interpolates the reference variable in accordance with the acceleration capacity of the sheet-fed printing machine and with a preselected rotational speed.
It is also advantageous if the closed-loop control of each drive is designed in a cascading arrangement made up of a closed-loop control of position, rotational-speed, and power. The highest precision is achieved using an open-loop drive control according to the present invention in accordance with a further specific advantageous embodiment, such that every closed-loop control of a drive has the same delay time constant.
The delay times can be reduced and the vibrations dampened in a particularly advantageous manner due to the fact that each closed-loop control of a drive has a rotational-speed and power pilot control (precontrol) for reducing delay times.
If set-up, cleaning, or maintenance work is to be carried out on a conventional sheet-fed printing machine having a central drive, then all the cylinders must be moved synchronously, as a result of which such tasks cannot be carried out in parallel, thus impairing machine amortization.
This problem can be circumvented by providing a drive control according to the present invention in which the closed-loop control R_MG1 . . . R_MG4 of each rubber cylinder G1 . . . G4 or closed-loop control R_MP1 . . . R_MP4 of each plate cylinder P1 . . . P4, instead of obeying common reference variable A_Soll, obeys a reference variable A_P1, A_P2 of its own, separate from a sheet-travel motion.
Further advantages and details of the present invention are provided on the basis of the following description of an exemplary embodiment and in connection with the Figures. In this context, elements having the same functionality are designated using the same reference numerals.